Hard disk drives are used in almost all computer system operations. In fact, most computing systems are not operational without some type of hard disk drive to store the most basic computing information such as the boot operation, the operating system, the applications, and the like. In general, the hard disk drive is a device which may or may not be removable, but without which the computing system will generally not operate.
The basic hard disk drive model was established approximately 50 years ago and resembles a phonograph. That is, the hard drive model includes a storage disk or hard disk that spins at a standard rotational speed. An actuator arm or slider is utilized to reach out over the disk. The arm has a magnetic read/write transducer or head for reading/writing information to or from a location on the disk. The complete assembly, e.g., the arm and head, is called a head gimbal assembly (HGA).
In operation, the hard disk is rotated at a set speed via a spindle motor assembly having a central drive hub. Additionally, there are tracks evenly spaced at known intervals across the disk. When a request for a read of a specific portion or track is received, the hard disk aligns the head, via the arm, over the specific track location and the head reads the information from the disk. In the same manner, when a request for a write of a specific portion or track is received, the hard disk aligns the head, via the arm, over the specific track location and the head writes the information to the disk.
Over the years, the disk and the head have undergone great reductions in their size. Much of the refinement has been driven by consumer demand for smaller and more portable hard drives such as those used in personal digital assistants (PDAs), MP3 players, and the like. For example, the original hard disk drive had a disk diameter of 24 inches. Modern hard disk drives are much smaller and include disk diameters of less than 2.5 inches (micro drives are significantly smaller than that). Advances in magnetic recording are also primary reasons for the reduction in size.
One of the processing steps performed in manufacturing the head includes ion milling. To prevent heat damage to the heads during ion milling, cooling is performed. Conventional pallet designs for ion milling use o-ring seals to prevent cooling gas, such as Helium, from leaking through these o-rings and into the ion milling chamber atmosphere.
Cooling gas leakage can cause a number of problems. First, the cooling of the pallet is greatly reduced when the cooling gas escapes past the o-rings, which can lead to damaged parts. Second, the leakage affects process stability because the ion milling chamber pressure is changed due to the cooling gas in the atmosphere. Third, since ion milling is usually performed in a vacuum environment, cooling gas leakage changes the atmospheric conditions which can lead to inconsistencies in the product.